FILE - In this Jan. 8, 2014 file photo, Sen. Marco Rubio, R-Fla. speaks on Capitol Hill in Washington. Rubio is positioning himself as the leading foreign policy hawk among Republicans considering runs for the White House, pushing for more military spending and greater intervention abroad as the United States confronts Islamic State extremists in Iraq and Syria. (AP Photo/J. Scott Applewhite, File)
(The Associated Press)

MIAMI – Sen. Marco Rubio called Wednesday for boosting U.S. defense spending and greater intervention abroad, positioning himself as the leading foreign policy hawk among Republicans considering runs for the White House.

"The world needs American strength just as much as our people and our economy do," Rubio told a conservative gathering in Washington. "No other nation can deter global conflict by its presence alone."

The Florida senator and potential Republican presidential candidate voiced support for President Barack Obama's strategy to arm moderate Syrian rebels battling Islamic State militants — but warned that American combat troops may be necessary to stop the march of extremist forces across the Middle East.

"We must be prepared for threats wherever they arise, because our nation is never isolated from the world," Rubio said. "Foreign policy is domestic policy."

Those positions create a contrast with some of his potential GOP rivals who remain wary of American intervention and could help repair Rubio's relations with conservative activists upset over his support for an immigration overhaul last year. The tough talk about fighting Islamic State extremists also could quell concerns among a broader swath of Republicans about the 43-year-old freshman senator's inexperience in global affairs — seen as a key vulnerability if Democrats nominate former Secretary of State Hillary Rodham Clinton in 2016.

Republican leaders see Obama's focus on winding down wars in Iraq and Afghanistan and a reluctance to use force as ripe for GOP critique in the coming presidential campaign. But some worry that their party's crop of young lawmakers would make less-than-convincing messengers.

Rubio's focus on foreign policy "allows someone who was the speaker of the House in Florida to preface his answers with, 'I said to the king of Jordan' and 'The prime minister of Japan said to me,'" said Elliott Abrams of the Council on Foreign Relations. "That kind of statement is important when you're trying to prove, 'I know what I'm talking about.'"

There also is significant political risk. Recent polls show strong public support for military action in Iraq and Syria. But public opinion can swiftly change after a decade of conflict in Iraq and Afghanistan. Experts forecast a prolonged campaign against a terrorist group that spans several countries.

"Most Americans are not only war-weary but very wary of being left with a hostile situation and really no civil government that's there on the ground," said Richard Lugar, the former Republican senator from Indiana who led the Foreign Relations Committee.

In recent months, Rubio has used his perch as one of only two Republican senators on the Foreign Relations and Intelligence committees to push for robust engagement on the world stage. He advocated tougher sanctions against Russia after its annexation of Crimea and its incursion into Ukraine and now wants the U.S. government to crack down on Venezuelan officials for human rights violations.

In his address Wednesday, Rubio sharply criticized Obama for cuts in defense spending and plans to shrink the U.S. military, arguing that while the nation's enemies have been modernizing and expanding their forces, the administration "was busy stripping parts from the engine of American strength."

Notably, he did not outline how he would pay for his proposal to grow U.S. forces, but insisted the military is "not the place to take costly short cuts" in deficit reduction.

Rubio also lashed out at the president -- and his potential GOP presidential rivals -- for opposing intervention in Syria until this month -- something Rubio has long advocated.

"Too many leaders in both parties, including our president and some who aspire to be president, have shown they would rather wait for poll numbers to change than to demonstrate the leadership necessary to shape them," he said.

Obama resisted military engagement in Syria for more than three years, wary of dragging the U.S. into yet another seemingly intractable Mideast conflict. He avoided arming rebels who oppose President Bashar Assad out of concern those weapons could fall into extremist hands. With the public opposed to intervention at the time, even Rubio rejected giving Obama authority to use missile strikes last year, saying the administration had waited too long to intervene.

The growing threat from Islamic State militants and the beheadings of two American journalists have changed those calculations.

For now, with recent polls showing majorities of Americans in both major political parties supporting plans for a military campaign against Islamic militants in Iraq and Syria, some GOP critics have begun to echo Rubio and other hawks in the party.

Earlier this month, Sen. Rand Paul, R-Ky., who had been skeptical of U.S. airstrikes, argued for some military force against the extremists in an opinion piece in Time magazine under the headline, "I Am Not an Isolationist." And Sen. Ted Cruz of Texas, another possible presidential contender who had been reluctant about American intervention, recently told activists at a conservative conference, "We ought to bomb (the militants) back to the Stone Age."

Unlike Rubio, however, Paul and Cruz oppose arming Syrian rebels, citing concerns about the ability to identify moderates in a country awash with rebel formations and shifting alliances.